1. Field of the Invention
The invention relates to humate and its use in printing ink and coating compositions. More particularly, the invention relates to the use of humate compositions as components of printing and colorant coating compositions.
2. Brief Description of the Prior Art
A wide variety of organic and inorganic materials have been used over the centuries as components of printing and coating compositions.
For example, humic acids have been suggested as useful pigments in printing and compositure; see for example Steelink, Proceedings of the California Assoc. of Chemistry Teachers, Journal Chem. Ed. Vol. 40, No. 7, July 1963, pg. 379.
The term "humic acid" has been widely applied to acidic solids obtained from plant decompositions. More recently, humic acids have been regarded as the intermediate product or products which result in the conversion of lignin and other plant materials to hard coal. It is believed that in the decomposition of vegetable matter, the portion of the cell wall material consisting largely of lignin is converted into humus. In time, the humus may be converted progressively to peat, brown coal, bituminous coal and finally into anthracite. More usually, "humic substance" is applied as a generic term for the organic acids derived from humus or the top layer of the soil, containing organic decomposition products of vegetation and animal organisms in admixture with inorganic compounds, sand, minerals, metal hydroxide bases etc. The chemical structure of the humic acids has not been established, but they are believed to be large condensed ring, polymer-like molecules containing pendant carboxylic and phenolic groups. Depending on their solubilities, humic substances are usually classified as humic acid, fulvic acid, hymatomelanic acid or humin.
The term "humate" as used throughout the specification and claims refers to the product of decayed plant and animal material (humus). The preferred humate employed in the method and compositions of the invention are generally derivatives by the natural flocculation or precipitation in sand deposits, of humic substances that were derived from natural humus found in association with earth sources. A most preferred source of humate is one derived from humic substances found in association with titanium mineral deposits.
In spite of the multitude of materials known to be useful as ingredients of printing inks and coating compositions, there has been a search for new materials, especially those suitable for aqueous inks, etc. We have discovered that humate has certain advantages, when used as an ingredient in ink and coating compositions. Humates dispersed in water may be used as a printing ink to transfer an image onto cellulosic substrates. The humates may be dispersed in water and transferred to paper in much the same way as carbon black is dispersed in mineral oil to produce a letterpress news ink.
Humates are relatively inexpensive and readily available. Other advantages associated with their use in ink and coating compositions will be described more fully hereinafter.